IL31283A - Liquid mixing and transfer structure and method - Google Patents

Description

LIQUID MIXING AND TRANSFER STRUCTURE AND METHOD The field of the invention herein is that which uses vessels and connecting conduits for the intermixing and the transfer of fluids primarily for the purpose of making measurements and tests on said fluids. In medicine, biology, ■' ' e chemistry and allied fields, research as well as routing: tes ing requires the use of apparatus which classically has been termed "glassware" or even "hardware", such as test tubes, beakers, bottles, retorts, pipets, and stills.

In recent years automatic chemistry apparatus has be-come popular, especially where testing, measurements and complex routines are to be repeated over and over again, but with different samples. Such apparatuses are used in chemi¬ cal analysis, chromatography, spectrophotometry, as well as in the measurement and analysis of biological specimens.

Automatic apparatus is required to draw in fluids, to dilute concentrates and mix liquids. In the case of blood sampling, multiple dilutions must be made, red cells must be lysed for making white cell determinations, liquids must be pumped, transferred, and moved between vessels. The manual techniques which are classically used in conventional work are not satisfactory, and the vessels and %uipment of the ordinary laboratory are not suitable for automated apparatus. Although glassware has been developed to meet the demand for apparatus which operates automatically, the basic requirements of automatic apparatus have produced problems which are believed not fully solved by the glassware which has thus " The most difficult problem is that of handling a plurality of fluids on a continuous basis. A continuous flow device would be the most satisfactory from an automatic machinery standpoint, such that it would repeat the same tests over and over again on the continuously flowing sample and provide the desired results. Unfortunately, the usefulness of such a device is manifestly limited, because the technician must know the test parameters for each of a series of completely different samples. When testing different samples the machine must handle each sample separately; hence, it is a batch device, but must be capable of routinely, quickly and continuously operating on sample after sample, giving the results accurately and without confusing the several samples. Accordingly, the problem arises of keeping the samples separate from one another, and this in turn requires absolute control of the handling of the samples.

The invention has as one of its important advantages the provision of method and apparatus which enables simple and complete transfer of liquids from one vessel to another with increased accuracy, and a minimum of contamination.

An important advantage of the embodied method and apparatus provides for the introduction of liquids into vessels which already contain liquids, or along with other liquids, in a manner which results in a minimum of turbulence, but which enables the liquids to be intermixed while entering and additionally after entering. simultaneously through the use of gas under pressure. By suitable. arrangements in combination with the liquid vessels and conduits, the gas under pressure is used for transferring liquid from one vessel to another or out of a vessel and -for mixing fluids. Accordingly, an advantage of the disclosed method and apparatus relates to the manner in which the gas in controlled, as for example in draining a vessel. While the major portion of the liquid remains in the vessel, the pressure of the gas above the liquid, which is forcing the liquid out of the drain, is at a maximum to speed the evacuation of the vessel. By suitable regulation, the pressure of the gas is gradually lowered as the vessel empties; until at the last instant, the pressure is practically zero, so that the draining occurs completely and yet without forcing gas through the drain to burst into the following receptacle for the fluid.

In particle analysis apparatus pioneered by Wallace H. Coulter and now known throughout the world under the name of "Coulter Counter", particles, such as red and white blood cells, are scanned as they pass with liquid through an aperture of very small dimensions simultaneously with the passage of an electric current through such aperture. Such scanning aperture and related elements are normally incapable of distinguishing between small bubbles and small particles, both in the order of a few microns. Hence, in apparatus of the type where counting, sizing and comparative analysis o o und i b o ha bubb any kind. Even optical counting can be rendered inaccurate by reason of the presence of bubbles. Many types of bubbles produced by turbulence during introduction, intermixture, dilution, transfer and similar handling of fluids are transient and disappear quickly, but the trouble arises with those bubbles that persist. Many chemicals promote bubbles, such as lysing agents which are used to break up the red blood cells so. that white cell measurements may be made. The embodied method and apparatus of the invention is especially useful to prevent the formation of bubbles that persist.

It has been found that larger bubbles move through liquids quickly and can be considered of a transient nature. These are desirable and can be used for mixing purposes, since they disappear without difficulty after rising to the surface of the body of liquid in which they are formed. The undesirable bubbles are the small ones which can even be microscopic in size, do not readily rise to the surface, do not readily break, and often move with liquids through passageways. They cause inaccuracies when liquids containing the same are measured. They cause false counts and signals in electronic particle detecting devices and generally can also cause contamination by adhering to vessel and conduit walls .

Disclosed hereinafter is the construction of apparatus in which the formation of tiny, undesirable bubbles is substantially inhibited and large, mixing bubbles are formed Also taught hereinafter is the use of gas pressure for the purpose of transferring liquid out of a vessel to another vessel or portion of the associated apparatus.

Thus, considering two vessels, comprising a first vessel which has liquid being introduced into it, and a second vessel which is connected to the first by way of a conduit connected to the drain of the first vessel and entering the second vessel at a tangent, it has been devised that gas pressure keeps the entering liquid from going into the connecting conduit while at the same time furnishing bubbles for mixing the liquid in the first vessel. There is an outlet port in the upper part of the first vessel to permit escape of gas, and an inlet port in the upper part of the second vessel by means of which to introduce the gas.

These ports conveniently can be connected to a gas control apparatus and can serve in several capacities. When the intermixture has been completed and it is desired to transfer the liquid from the first vessel into the second, the ports are interchanged by the gas control apparatus. The port of the first vessel is connected to a source of gas pressure and the port of the second vessel is connected to exhaust.

Accordingly, the invention provides /structure for automatically handling liquids in a mixing and transfer apparatus, which comprises at least a first vessel having a liquid entrance port spaced substantially above the level of liquid after liquid has fully entered and been retained in the vessel, said liquid entrance port constructed to direct an entering stream of liquid against the inner surface of the vessel while imparting a horizontal component of rotary liquid motion so as to cause most of the liquid to flow along said surface before collecting /at the bottom of the vessel, a vertical component imparting arrangement for imparting a vertical component of mixing motion to liquid means in said vessel, and e©fnp©ffeT-¾¾ for draining liquid from said vessel after mixing, including an outlet at the bottom of said vessel.

The invention further provides a method for mixing liquid entering near the top of a first vessel and thereafter draining the mixed liquid from a drain at the bottom thereof which comprises: directing an entering stream of liquid into said vessel on substantially a tangential path relative to the interior wall thereof so that the liquid is thereby given a primarily horizontal rotative component while it collects at the bottom of the vessel and a vertical component due primarily to gravity.

The preferred embodiments of this invention will Figure I is a schematic diagram showing a portion of an automatic fluid handling system which includes structures according to a primary embodiment of the invention Figure 2 is a side elevational view of a piece of glassware, formed of two separate vessels, a portion being broken away and shown in section, and constructed in accordance With a primary embodiment of the invention; Figure.3 is a sectional view taken generally along the line 3-3 of Figure 2 and in the indicated direction; Figure 4 is a sectional view taken generally along the line 4-4 of Figure 2 and in the indicated direction; Figure 5 is a schematic diagram illustrating a structure constructed in accordance with another embodiment of the invention; Figure 6 is a schematic diagram illustrating generally a structure which can be operated in different manners, depending upon the presence or absence of certain connections and valves, the view being more for explanatory purposes than for illustrating any particular form of structure; and Figure 7 is a schematic diagram illustrating a structure using a single vessel, such illustration being used to describe another embodiment of the invention.

In Figure 1 there is illustrated a system for the handling of liquids, for the purpose of processing a sample of whole blood or the like to ascertain certain sample parameters by measurements and computation. Vessels which are . they are intended to operate in pairs as in this diagram, single vessels can be used under many conditions. Also provided are liquid sources 18, 20 and 22, which can contain items such as blood sample, first diluent and second diluent, respectively and generally to be identified as sources A, B, and C, respectively. A mixing valve 24- comprises an arrangement of metering valves for controlling the introduction of liquids .into the system. Such valve would also include apparatus , such as pumps , conduits , and the like. A program and control center 26 provides overall control for the entire system, and its control over the mixing valve 24 is by way of a control line 27.

Consider that measurements are to be made of blood indices, such as white and red blood cell counts. The mixing valve 24 draws in a sample of the liquid source A at 18 by > way of a line 28 and introduces a precise quantity of the sample along with a precise quantity of diluent into the first vessel 14 by way of a line 30. The diluent would be obtained- from the liquid source B at 20 by way of a line 32. Gas under pressure is applied to an inlet port 34 by a line 36 to the interior of the vessel 16 at the top thereof, fills the vessel 16, and passes out the bottom end thereof. Control over the gas is achieved through a suitable gas valve 40 which receives its supply from a line 42 and is programmed by way of a line 64 from the program and control center 26.

Entry via the line 38 into the vessel 16 of the two li uids flowin into the vessel 14 is controlled by the the time that. the liquids start to flow into the vessel 14, gas is emerging into the bottom of the vessel 14 by way of the line 38 and is leaving by way of a port 44 and a line 46. The liquids introduced by the mixing valve 24 remain in the vessel 14 and are thoroughly mixed by the large bubbles which rise from the line 38. Preferably, the apparatus is adjusted so that these bubbles are visible, on the order of 1,000 to 3,000 microns in diameter, causing them to rise very fast and disappear quickly. Undesirable bubbles substantiall smaller than that dimension, could remain in suspension long enough to be counted later as particles and could adhere to the walls of the vessels and conduits and cause intersample contamination.

After a time controlled by the program and control center 26, the derived and mixed liquid in the vessel 14 is permitted to pass through the line 38 into the vessel 16 where additional mixing occurs. The gas valve 40 converts the ports 34 and 44 from inlet and outlet, respectively, to outlet and inlet, so that pressure is applied upon the vessel 14 above the liquid body therein and forces the same through the line 38 into the vessel 16. In transferring the liquid from the vessel 14 to the vessel 16, the pressure is reduced in a progressive manner, such that as the volume of liquid in the vessel 14 decreases, the pressure decreases, preventing a violent stream of bubbles from being shot into the body of liquid in the vessel 16 at the end of the transfer and et all of the liquid is transferred. After the slowly into the vessel 16 in order to produce additional intermixing; although, introduction of the liquid at the bottom of the vessel 16 does provide mixing while transfer is occurring. After the liquid in the vessel 16 has been thoroughly mixed, a portion of the liquid is removed by a siphon 48 that dips down into the vessel 16.

It will be understood that for purposes of the stated example the first dilution was made to produce a dilution of blood cells which is to be eventually limited to white blood cells. Since the red blood cell count must be made at a much higher dilution of the same sample, a dilution is made . of the first dilution and this is the reason for withdrawing a small portion of the liquid from the vessel 16 by way of the siphon 48 which is connected to the mixing valve 24 by way of a line 50. The liquid from the line 50 is transferred into the mixing valve and, by way of a line '52, is directed into the vessel 10, which is the first vessel of the pair interconnected by a conduit 54. The mixing valve 24 dilutes the liquid in the line 50 which passes through it by means of the other diluent obtained from the source C at 22 by way of the line 58.

In the vessels 10 and 12, the same process of intermixing and transferring occurs as described in connection with the vessels 14 and 16. A gas valve 60, also controlled by the program and control center 26 by way of a control channel 62 serves the same function as the gas valve 40. 36 and 46 and operate in the same manner. Discharge from the vessels 10 and 12 occurs through an outlet drain 73 and a valve 74, and is under the control of the program and control center 26 by way of a control channel 76. The result-ing red blood cell dilution is passed to a suitable counting device or measuring apparatus R designated by a block 77.

As for the liquid in the vessel 16, since this liquid is to be used.for the white cell determination, it is first passed out of a drain 78 through a valve 79, which is controlled by a control channel 80, is passed into a line 82 and thence into a lysing vessel 84. This vessel would also employ gas under pressure for mixing, holding and transferring. Additionally, a second fluid is introduced into the vessel 84 by way of a line.86 from a fluid pump 88, which brings a source of liquid D from a fourth liquid source 90 under the control of a control channel 92, also operated by the program and control center 26. The liquid which is introduced in the line 86 is a lysing agent. . After lysing, the resulting fluid is run out through a valve 94 to a line 95 which carries the same into a meas-uring apparatus W designated by a block 96. The valve 94 is operated by means of a control channel 97 from the program and control center 26.

A gas source 43 serves as a supply for the entire apparatus. Such source, which can be air, is connected. to the several gas valves 40, 60 and 89 by the lines 42. Also, each gas valve has an exhaust for conventional operation.

B means of a line 99 as is introduced from the as valve 89 or is exhausted from the vessel 84. Operation of the valve 89 is controlled from the center 26 via the channel 98.

In transferring fluids attention might be drawn to the use of a line which passes out of a vessel and into another at a higher level so that a pressure head is required to be overcome to pass the fluid. This is easily accomplished by the use of the gas under pressure as described and, additionally, the line is blown free of the liquid. No valves are needed in such case, and by suitable control of the gas, very accurate control of the liquid movement is achieved.

Other portions of the apparatus do require valves of different kinds and most of them are of an automatic variety readily available commercially.

In Figures 2, 3 and 4 the details of the structure of a dual vessel mixing device are shown. This comprises the structure including the vesselsί4 and 16. The vessels are shown capped at 100 and 102 for use in the manner contemplated; although, it will be understood that the basic concept of tangential entry of fluids can be used with open vessels.

A fitting 104 is shaped to join with the wall of the vessel 14 so that its bore 106 enters the interior of the vessel tangential to the inner surface, as best shown in Figure 3.

Also, the angle of the bore 106 is such that the entering stream of liquid from the line 30 is pointed slightly down-ward. When liquid enters the vessel, it spreads smoothly on the interior surface of the wall of the vessel, wetting the wall and swirls downwardl in a helix as indicated b bottom with a minimum of turbulence and hence a minimum of minute bubbles.

As previously explained, the gas under pressure is forced into the chamber 16 by way of the port 34, enters the bore 110 of the conduit 38 and emerges at a drain hole 112.. The gas prevents the liquid gathering in the bottom of the vessel 14 from entering the bore 110 so long as the pressure is applied, and large gas bubbles rise up from the drain hole 112 through the liquid (see, for example, Figure 5) thereby mixing the liquid in an up-and-down movement. The gas then passes into the space above the liquid in the vessel 14 and out through the port 44.

When the liquid is transferred from one vessel to another, the ports 34 and 44 change their functions. Pressure is applied through the port 44 and gas permitted to escape through the port 34. The liquid is forced through the bore 110 and i enters the bottom end of the vessel 16 at 114 (Figure 4) also on a tangent, so that there will be a minimum of turbulence in transfer. Since the valve 79 is normally closed at this time, the liquid accumulates in the bottom of the vessel 16, and the liquid entering at 114 creates a swirling pool which thoroughly mixes the liquid. Due to the small diameter of the path 78, the liquid is excluded from it by the entrapped gas above the valve 79. As explained, the liquids introduced into the vessel 14 can comprise a small volume of highly concentrated liquid and a diluent, and where a thorou h mixin is to be assured the use of two The first vessel 14 has the inlet fitting 104 substantially above the level of the liquid. This assures a minimum of. contamination, since only the diluent which follows the sample can come in contact with the inlet. This arrange-ment is. preferred, because of the paramount importance of freedom from contamination. The siphon 43 has its entrance slightly below the level of the entrance 114 to prevent the possibility of bubbles being drawn into the line 50.

Figure 5 illustrates a single mixing vessel 120 which has an inlet fitting 122 similar to the fitting 104 in Figure 2, so that liquid is introduced into the vessel 120 tangen-tially along the broken line 121, which is in the form of a helix. A gas port 124 at the top of vessel 120 enters through a cap 123, and gas from a source, not shown, is received on a line 125 controlled by a gas control element 126. The gas can be introduced or exhausted by way of a line 127 or can be introduced in a drain 128 by way of a line 130, also controlled by the gas control element. The introduction of gas into the drain 128 produces large bubbles which rise through the body of liquid and, while preventing the liquid from entering the drain 128, also serves to mix thoroughly the liquid by an up-and-down movement represented by small broken arrows 132. Gas is exhausted from the gas control element by way of an exhaust line 134. An outlet valve 146 enables transfer of liquid through drain 128, and is programmed in any suitable manner by a control channel 147. ' suitable for a wide variety of applications. Thus, considering only the equivalent structure shown in Figures 2, 3 and 4, the same is identified in Figure 6 by the prefix "6" using the same characters of reference. Mirror structure is provided for versatility, identified by the prefix "6" and a prime being added to the same characters of reference. In addition to the structure mentioned there are shown inlet ports at.601 and 601' for enabling the introduction of liquid, from external sources into the interior of the respective vessels, and a plurality of valves. These valves are designated VI, V2, V3, V4 and V5 and their control is obtained from program and control elements which are not illustrated. Gas pressure is used to assure proper liquid transportation. It may be assumed that the same constructional details are used in forming this device and that some of the parts can be omitted or further duplicated. Entrance ports 604 and 604' are tangential; the dimensions of the vessels are such that the minimum wall surface consistent with good mixing is contacted by the volume of fluid to be handled; port entrances at the bottom of the vessels are tangential to promote swirling movement upon entry of liquids; and the size of conduits draining and communicating between vessels is optimum so that capillarity due to too small diameter conduits is avoided. On the other hand, the conduit size must be small enough so that gas can be used to control the fluid.

This dimension for structure handling blood dilutions is In Figure 6, many different schemes of operation can be utilized. : For example , with the valves VI, V2, V3 and V4 closed, gas being introduced at 636 and the valve V5 connecting only the line 6114' with the line 638, liquids can be introduced at 604 and/or 601. Bubbles will enter the drain 6112 and mix the liquid in the vessel 614 and escape through the port 646, which here acts as an exhaust. No liquids are introduced at 6041 or 6011. If desired, the valve V5 can be arranged to enable the gas during this period of time to pass by way of the drain 6112' and the line 638' into the vessel 614.

After the liquid has been sufficiently mixed, the gas ports 636 and 646 are changed, so that gas is introduced at 646 and exhausted at 636. The liquid from the vessel 614 passes into the vessel 616 along any chosen path, depending upon the construction and operation of the valve V5. After entering this vessel, additional liquids can be introduced at 604' and 6011 and additional mixing can take place, not only during entry of the liquids, but even afterwards, b permitting the gas to continue to bubble through the liquid either from the entrance line 6114' or by way of the line 638' . Thereafter, by suitable valve manipulation and gas control, the liquid can be discharged through the drain 678' and the valve V3.

During this period, it is feasible to introduce additional gas at 678f through the valve VI for mixing or the like. ossible arran ements and ro rammin will be Figure 7 illustrates a novel valve system which embodies the invention, illustrating especially the manner in which a tapered gas pressure can be achieved for drainage purposes, as explained above.

The vessel 160 may be considered the equivalent of a vessel such as illustrated in Figure 5 and it is provided with a gas port 162, a liquid inlet port 164 near the top of the vessel, a drain 166, a lower gas inlet port 168 and valve 169, and outlet valve 170. The construction of the elements thus far mentioned is as previously described.

A source of gas 172 is connected by a line 174 to a pressure regulator 176 that controls the pressure of gas which is run into pressure vessel.178. The pressure regulator is connected to the pressure vessel 178 through a two-way valve 180 by interconnecting lines 182 and 184. A program and control center 186 has control channels to various parts of the apparatus, as indicated at 188, 190, 192 and 194. The pressure vessel 178 is connected by a line 196 to a manually adjustable needle valve 198, which in turn operates through a line 200 to pass the gas to a three-way valve 202. This three-way valve 202 is connected to an exhaust line 204 in such a manner as to enable the gas inlet port 162 in vessel 160 to be connected by way of a line 206 with the exhaust line 204 or the gas pressure inlet line 200. The pressure regulator 176 also controls the gas pressure through a manual needle valve 210 by way of a line 208. The gas passing through the needle valve 210 is passed to the valve 169 by a line 212.

When liquid is entering the vessel 160 through the inlet 164, the valve 170 is closed, this condition being achieved by the control channel 194 which can be operated by the control center 186 or some other control element in a different part of the system. The valve 169 is open under control of the program and control center 186 by way of the channel 190 so that it is connected by the line 212 with the manual needle valve 210 which is receiving gas under pressure from the source of gas 172 either through the pressure regulator 176 or some other regulator by way of the line 208. Thus, gas can be bubbled through the drain 166 into the body of liquid and mix the same, while preventing any of the liquid from moving down into the drain. This gas will leave the system through exhause 204, along with the gas in vessel 160 displaced by the entering liquid. To achieve the highest quality of mixing, it is desirable to maintain the valves 169, 170, and 202 in this mode of operation until all the prescribed liquid enters and until the swirling of the liquid body subsides . · When the liquid has been thoroughly mixed, the valves 169, 170, and 202 are operated to their second states to achieve emptying, by signals from the program and control center 186 through the control channels 190, 194 and 188.

Structure is provided to prevent the escape of gas from the fluid inlet 164 by such expedients as the positive displacement pump 88 and the mixing valve 24 of Figure 1.

The condition of the s stem in this state is as follows: drain 166. The valve 170 is opened to allow liquid to pass out of drain 166 through a tube 171 to the next stage of sample processing not illustrated in Figure 7. The three-:: way valve 202 is ported to allow gas through needle valve 198 to pass into the vessel 160 by way of the lines 200 and 206 through the port 162. In addition, the two-way valve 180 is opened by means of the control channel 192 from the program and control center 186. Thus, the pressure vessel 178 is filled with gas at a pressure that is controlled by the regulator characteristics. This could be a value such as 5 pounds per square inch.

Due to this pressure in the vessel 178, the needle valve 198 allows gas to flow into the vessel 160 at the port 162 through the three-way valve 202 and create a gas pressure above the fluid level in vessel 160, which is adjustable by the needle valve 198 to the magnitude required to force the liquid in the vessel 160 out of the drain 166 and along the tube 171 at the desired rate of speed.

This portion of the liquid transfer operation maintains a constant liquid transfer rate out of the drain 166 and the tube 171 because of the following conditions: When the tube 171 is full of liquid moving at a given velocity, the friction between the liquid and the wall of the tube 171 has a given value, and the pressure drop across the needle valve 198 stabilizes at a substantial value. The force applied by gas in the vessel 160 onto the surface of the liquid therein is the onl force applied to the system other than gravity.

If the frictional forces encountered in the tube 171, which in acting against the remaining gas pressure force in the vessel 160, is equal to the gas pressure force and the force of gravity, there, occurs no net gain or loss in the flow velocity. So if there is a constant liquid flow velocity through the tube 171 there must be a constant gas pressure force in the vessel 160 above the remaining liquid. This implies .that there must be a constant gas pressure acting upon the liquid to achieve the condition of constant flow.

Since the gas occupied volume of the vessel 160 is increasing as the liquid leaves the drain 166, a uniform flow rate of gas into the port 162 is necessary to maintain the gas pressure at a constant level in the vessel 160. The constant flow is accomplished by the pressure regulator 176 and the needle valve 198 which are at this time connected to the vessel 160 by the lines 206, 200, 196, 184 and 182 and the components 202, 178 and 180.

This constant rate of liquid transfer is maintained by the program and control center 186 until the vessel 160 is almost empty, at which time the program and control center 186 signals the valve 180 to change state by way of the control line 192. This causes the previously mentioned tapered decrease in emptying velocity from the vessel 160 through the tube 171 so that the velocity of the existing liquid becomes practically zero by the time the last drop of liquid emerges from the tube 171. and in the needle valve 198 are large with respect to the inertial forces due to the mass and velocity of the various fluids. When this is the case, the pressure used to accomplish this is also substantially zero. However, if the mass and/or velocity of the fluid is so large that inertia is not negligible, the capacities of gas occupied volumes can be . adjusted. so that a negative or braking force is applied to the liquid surface at this time.

Braking action is accomplished in the following manner: 10 At the proper moment the two-way valve 180 is shut off by means of the control line 192 from the program and control center 186. As gas from the pressure vessel 178 escapes •f ? through the needle valve 198 the pressure in the vessel 178 begins to decrease. As this pressure decreases, the flow . rate of gas through the needle valve decreases and hence the flow rate of gas into the vessel 160 decreases. When this happens, the pressure in the vessel 160 decreases, which causes a decrease in the force on the remaining liquid in the vessel 160 and hence a decrease in the flow rate of liquid out of the tube 171. This continues until there exists no more pressure in the pressure vessel 178. The adjustment of the system is accomplished by the adjustment of the needle valve 198, which effects this stage of emptying along with the previous stage of constant flow emptying of the vessel 160, so that for a set of given conditions of program, control time, and pressure vessel size, a satisfactory

Claims (30)

V What we claim is:

1. Structure for automatically handling liquids in a mixing and transfer apparatus, which comprises at least a first vessel having a liquid entrance port spaced substantially above the level of liquid after liquid has fully enter£d and been retained in the vessel, said liquid entrance port constructed to direct an entering stream of liquid against the inner surface of the vessel while imparting a horizontal component of rotary liquid motion so as to cause most of the liquid to flow along said surface before collecting at the bottom of the vessel, a vertical component imparting arrangement for imparting a vertical component means of mixing motion to liquid in said vessel, and 8Bmp©iHS»*3S for draining liquid from said vessel after mixing, including an outlet at the bottom of said vessel.

2. Structure according to claim 1 which further comprises, a second vessel connected to said first vessel for combined liquid transferring functioning, said first vessel having a first gas port at its top and its liquid entrance port and outlet being termed a first liquid entrance port and a first drain outlet, said second vessel having a second liquid entrance port adjacent its bottom end, but substantially below the normal level of liquid to be retained therein, a second gas port at its top, and a second drain outlet at its bottom and substantially below said second liquid entrance port, and a conduit providing the said subsequent to the liquid being collected and mixed in said first vessel, it then can be transferred to the second vessel by way of said first drain outlet, conduit and second liquid entrance port, be mixed while being collected in said second vessel, and thereafter be expelled from said second vessel by way of said second drain outlet.

3. Structure according to claim 1 or 2 in which said vertical component imparting arrangement is constructed to prevent draining of liquid from said first vessel during operation of said arrangement.

4. Structure according to any one of claims 1 through 3 in which said vertical component imparting arrangement comprises a first source of gas of a pressure higher than that of gas above the liquid in said first vessel and connected to said first vessel at least at its outlet for forming a gas pressure differential for introducing bubbles into the bottom of said first vessel and thereby into the liquid in said first vessel.

5. Structure according to claim 4 in which each said vessel is enclosed except for its liquid entrance port and means its outlet, and said draining ¾©fflj?o¾

6. Structure according to claim 5 in which said gas sources are combined, said controller includes gas flow valves, and in which each said gas port is arranged to exhaust gas when gas is being introduced into its associated outlet.

7. Structure according to claim 5 or 6 in which said controller is arranged to change the pressure of said gas after the liquid in said first vessel is mixed, to cause the liquid from the first vessel to be expelled into said first drain outlet, through said conduit, and by way of said second liquid entrance port into said second vessel, and a valve is provided to block the second drain outlet of said second vessel until it is desired to drain the liquid therefrom.

8. Structure according to claim 7 in which said controller causes said first gas port to be an exhaust port and said second gas port to be an inlet port while said stream of liquid is entering said first vessel, and vice versa when said liquid is entering said second vessel.

9. Structure according to any one of claims 2 through 8 in which a siphon is provided to siphon liquid from said second vessel, said siphon opening to said second vessel above the second drain outlet and below the second liquid entrance port.

10. Structure according to any one of claims 1 through 9 in which each said vessel is substantially circular on its respect to the volume of liquid which is to be handled by the apparatus so that the surface contacted by the liquid when the entire volume of liquid has entered and been retained in the vessel is substantially minimized.

11. Structure according to any one of claims 1 through 10 in which the vertical component imparting arrangement includes a construction of said first liquid entrance port so that the stream of entering liquid is slanted downward.

12. Structure according to anyone of claims 1 through 11 in which the first liquid entrance port is arranged so that the stream of entering liquid has a component tangential to the transverse cross section of the first vessel.

13. Structure according to any one of claims 1 through 12 in which said first liquid entrance port and said vertical component imparting arrangement are proportioned with respect to one another to produce a maximum of swirling action for mixing purposes .

14. Structure according to any one of claims 2 through 13 in which the second liquid entrance port is arranged to direct an entering stream of liquid in a generally tangential direction relative to the bottom of the second vessel so as to produce swirling in the liquid being collected in the second vessel.

15. Structure according to any one of claims 2 through 10 in which said first and second vessels are arranged vertically, each forming a separate chamber, a conduit connects them at their bottom ends, one chamber is shorter than the other, whereby the connecting conduit is at an angle, an entering pipe is integral with the shorter chamber and has a bore disposed to direct the entering liquid stream at an angle downward and tangential to the inner surface of the wall of the shorter chamber, and the longer chamber has a drain at its bottom end.

16. Structure according to any one of claims 5 through 15 in which said controller tapers the effective pressure of said second gas source while the liquid is draining.

17. Structure according to claim 1 in which said first vessel has a first gas port at its top and a second gas port in. its bottom, and there are provided a source of gas under pressure, a gas pressure accumulator, a device for establishing a predetermined pressure in the accumulator from the source, and a gas control system connected with said accumulator and source and having connections with the vessel to introduce gas at the second port and exhaust it from the first port while liquid is being introduced into the vessel at the top thereof and accumulated in the bottom, said gas control system discontinuing the introduction of gas into the second port and connecting the accumulator to the first port, whereby to expel under pressure the liquid

18. ; Structure according to claim 17 in which the gas control system is constructed to disconnect the source from the accumulator when connecting said accumulator to said first gas port, whereby the pressure of gas above the liquid from said accumulator decreases while the liquid is being expelled from said vessel.

19. A method for mixing liquid entering near the top of a first vessel and thereafter draining the mixed liquid from a drain at the bottom thereof which comprises, directing an entering stream of liquid into said vessel on substantially a tangential path relative to the interior wall thereof so that the liquid is thereby given a primarily horizontal rotative component while it collects at the bottom of the •vessel and a vertical component due primarily to gravity.

20. The method according to claim 19 in which a second vessel is connected near its bottom to the drain of the first vessel which comprises, introducing the liquid into the first vessel while applying a first pressure differential between vessels effective through their bottom connection to prevent drainage of liquid from the first vessel into the second vessel, collecting and mixing the liquid in the first vessel while maintaining said pressure differential, applying a second pressure differential to expel the liquid from the first vessel to the second vessel with a swirling movement in the second vessel and collecting the liquid in the second vessel, and draining the liquid from the second

21. The method according to claim 19 or 20 which additionally comprises, directing the liquid stream into the first vessel in a downward slant.

22. The method according to claim 21 which comprises, optimizing of the downward slant for maximizing the resulting energy for mixing purposes.

23. The method according to any one of claims 19 through 22 which further comprises, introducing moving gas bubbles into the bottom of the first vessel to provide an additional vertical mixing component.

24. The method according to any one of claims 19 through 22 which comprises, introducing relatively fast-moving gas bubbles into the center of the first vessel at the bottom thereof while the stream of liquid is entering the top thereof, thereby preventing the liquid from draining from the first vessel and providing an additional vertical mixing component to said liquid.

25. The method according to claim 24 which comprises, continuing the introduction of bubbles after the liquid has entered the first vessel but before it is drained.

26. The method according to any one of claims 23 through 25 which, after the liquid has been mixed, comprises, discontinuing the introducing of bubbles and applying a gas pressure above the liquid to expel the same from the first vessel through its drain.

27. The method according to claim 26 which further comprises, decreasing the gas pressure as the liquid drains.

28. The method according to any one of claims 20 through 27 which comprises, producing bubbles by said first pressure differential and causing such bubbles to pass from the second vessel through the connection into the bottom of the first vessel and thereafter rise through the liquid collecting in the first vessel.

29. An improved structure for handling and mixing liquid substantially as described with reference to the accompanying drawings.

30. An improved method for handling and mixing liquid substantially as described with reference to the accompanying drawings . Aviv, dated this I day, December, 1968.